A great deal of interest has been directed towards the identification of tumor-specific antigens, however to date no such marker has been found. Our laboratory has taken the approach to identify normal adult organ-specific antigens which are retained and expressed only in the respective tumor type. We have identified such antigens in the colon, pancreas and stomach. These markers are present in about 50%-60% of the respective tumors. In each instance the immunodeterminant is a derivative of sialic acid present as a structural component of membrane glycolipids, and secreted mucin-type glycoproteins. In addition, we believe that a majority of tumors which do not express the organ-specific determinant, do express the immediate precursor structure which may also be organ-specific. The overall objective of the current proposal is the development of monoclonal antibodies directed against known, structurally characterized organ and tumor-associated immunodeterminants, for potential application in the diagnosis, management, and therapy of cancer. We will isolate the organ-specific antigens from colon, pancreas and stomach and biochemically modify them to obtain the precursor structures. Monoclonal antibodies will be prepared against each structure and utilized in immunoassays to examine the tissue distribution of the structures. Thus we hope to gain information which will lead to the development of procedures for diagnosis, classification and detection of GI cancer.